I created a calculator without effort. Copy mooncalc folder to your MicroSD then execute MoonCalc.nds .
You can input only in dec form(no bin/hex input), so this isn't so useful.
Launching from other than MoonShell ver 2.10 stable Zwai edition might cause no sound.
You can check mooncalc version by opening preference (by clicking the gray box or pressing SELECT) and seeing the upper right (in lower screen) ver x.xx
I got bored so perhaps there won't be an update unless a fatal bug.